The present invention relates to the disinfecting and sterilizing arts. It finds particular application in conjunction with compact steam sterilization systems used in hospitals, clinics, physicians offices, and other healthcare facilities as well as those used in pharmaceutical, laboratory, and other facilities.
Steam sterilizers are highly effective in sterilizing medical instruments and related items that are able to withstand the high temperature, high moisture, and high pressure within the steam sterilization chamber. Despite the effectiveness and popularity of steam sterilizers, the control systems for these devices have remained relatively large, non-integrated, and expensive. For example, a keypad for user input, a printer for hard copy output, and a visual display were connected to multiple circuit "cards" or boards that drive these input and output devices. The input and output boards were also connected with the main controller circuit board. These connections were provided through wiring harnesses and the like that increased the size of the control system and the sterilizer overall, increased material and assembly costs, and increased the number of electrical connections in the control system which led to unreliability.
Furthermore, typical compact steam sterilizer control systems have not included feedback systems to provide an added level of safety and effectiveness by ensuring that, when the controller initiated an operation; the operation was actually carried out. With prior systems, the controller could be unaware that a relay has failed in an open or closed position. The controller might energize or deenergize a relay coil without any actual relay operation being carried out. This could result in erroneous machine operations and, in certain instances, could result in an operator of the sterilizer being subjected to a dangerous condition.
Another drawback associated with prior steam sterilizer control systems was their lack of ratiometric circuitry. The high temperature within and surrounding known steam sterilizers caused the output signals from analog devices to drift. An analog-to-digital converter received a varying analog input signal from a pressure or temperature sensor and provided varying output data to the central processing unit of the control system depending upon the temperature of the sensor and the associated circuitry. With non-ratiometric control systems, one could not be entirely certain of pressure, temperature, and other analog measurements that are critical to effective and safe sterilizer performance.
Prior steam sterilizers utilized common tap water for steam generation in a boiler or the like. Commonly assigned and co-pending U.S. patent application entitled Steam Delivery System for a Decontamination Apparatus, filed on even date herewith and expressly incorporated by reference herein, describes a flash steam generator system for generating steam as an alternative to using a boiler. However, the flash generator uses filtered water to prevent fouling of the flash generator due to mineral deposits and the like. Prior control systems for steam sterilizers did not control the delivery of filtered water to a flash steam generator. Furthermore, prior control systems did not inform an operator when a water filter was due for replacement.
The present invention provides a new and improved method and apparatus for overcoming the above-referenced problems and others.